1. Field of the Invention
The present invention relates to a communication equipment, a communication system, and a communication method.
2. Description of the Related Art
Conventionally, a communication equipment that performs packet communication using an Internet protocol (IP) address uses one IP address for each communication. A communication procedure to be performed by a communication equipment to which an IP address is provided, respectively, is described as taking a host A and host B as an example. The host A sets its own IP address as the source address, and transmits to the host B a packet where an IP address of the host B is set as the destination address to start communication. After receiving the transmitted packet, the host B sets the source address included in the received packet as the destination address of the packet, and sets the destination address included in the received packet as the source address of the packet, and then transmits the packet to the host A. Through repetition of this procedure, the host A and host B communicate. Note that the route for packet reception/transmission is determined by routers that exist between the communication equipments, based on the source address or destination address of each packet.
In addition, an IP address is, normally, provided for each media in an IP network. For example, a local area network (LAN) forms one media, and an IP address is provided for each LAN. This is similar to the case of a wireless LAN, which has become more prevalent in recent years. The wireless LAN is an area network where a base station is connected to a fixed LAN, and where a mobile communication equipment having a wireless LAN card performs wireless communication with a LAN by connecting to the base station.
However, conventionally, a communication equipment can use only one IP address for each communication. As a result, a packet reception/transmission route determined by a router based on a source address or a destination address of a packet is almost always fixed to one route even though there may be a plurality of routes between communication equipments. Accordingly, a communication equipment cannot perform packet reception/transmission using a more preferable route or packet reception/transmission using a plurality of routes. As a result, effective data transfer cannot be performed.
In addition, if a srperate IP address is provided within each LAN, a communication equipment cannot use an IP address that is provided within one LAN, within another LAN. In a wireless LAN, the same IP address can be used if the communication equipment exists within the same wireless LAN area even if the communication equipment moves and changes the base station connection. However, in the case where the communication equipment moves outside the wireless LAN area, even if the communication equipment can find and connect to a new base station, the new base station connects to a wireless LAN, which is different from the previously connected wireless LAN. As a result, the communication equipment becomes unable to use the IP address provided for the previously connected wireless LAN.
Accordingly, the communication equipment must acquire a new IP address that can be used with the newly connected wireless LAN. Also, there is a problem in that the communication equipment cannot maintain prior communication. That is, the communication equipment cannot guarantee continuous mobile communication. Mobile IP has been proposed as a technology for solving such problems. However, a specific function for using Mobile IP must be provided for the IP network in advance.